1. Field of the Invention
The present invention relates to an optical fiber having distinctive layers composed of ink by which the optical fiber can be distinguished from the others, and to an optical fiber cable using the same.
2. Description of the Related Art
As transmission capacity increases in the field of optical communication, utilization of an optical fiber cable including many optical fibers therein is rapidly progressing. Accompanying this progress, it has been a requirement that the optical fiber itself has a multi-distinctive function, such that a workman can distinguish instantaneously each optical fiber composing an optical fiber cable. The following two methods for the above requirement have been conventionally employed. The first is a method where an optical fiber is distinguished from the others through coloring a coating resin itself such as polyamide resin, which covers an optical fiber core. The second is a method where an optical fiber is distinguished from the others through spraying ultraviolet-rays hardenable ink or thermosetting ink on the optical fiber core to form a colored layer. However, since the number of colors should be limited in the case where a distinction is made by coloring, these methods cannot cope with a sharp increase in the number of optical fibers composing the optical fiber cable.
Thereby, providing a new distinctive function for an optical fiber through forming further distinctive layers by spraying ink or the like intermittently in the longitudinal direction of the optical fiber on a colored layer, has been considered. However, in the case where a distinction is made by a distribution pattern of distinctive layers on the colored layer, the distinctive layers composed of ink or the like, are liable to be peeled off by being touched by something at this portion, and the distinctive layers composed of ink are also liable to be dissolved by coming into contact with chemicals, etc., resulting in the problem where the distinctive function of the optical fiber is neutralized by external factors.
Therefore, forming distinctive layers composed of ink or the like between an optical fiber core and a colored layer in order to obtain an optical fiber whose distinctive function is not neutralized by any external factors, has also been considered. Nevertheless, even in the optical fiber with such a structure, it has been pointed out that there is still a problem in that transmission loss of the optical fiber may be increased by the distinctive layers formed between the optical fiber core and the colored layer.